The present invention pertains to lifts for watercraft such as boats and sea planes.
Known in the art is U.S. Pat. No. 4,895,479, issued to Michaelsen, et al., which discloses a lift for a watercraft having a stationary base frame mounted under water and supporting generally upwardly extending, swingable parallel links. A lift platform supported at the upper end portions of the links, in combination with the base frame and links, forms a parallelogram. A hydraulic cylinder is connected generally diagonally of the parallelogram and has a plunger for swinging the links to translate the lift platform up to remove a watercraft from the water, or down to lower the watercraft back into the water. In its raised position, the lift supports the watercraft at an angle such that the swingable, parallel links are disposed under true vertical at about 70.degree.. In order to lock the swingable parallel links in this position, a dog or pawl engages and restrains reciprocation of the hydraulic cylinder. The dog or pawl locks in regularly spaced through-slots on the hydraulic cylinder plunger. This locking mechanism is at best unreliable and can be hazardous because mechanical failure of the dog or pawl results in unexpected lowering of the watercraft on the lift. Additionally, the requirement of this dog or pawl increases the mechanical complexity and cost of the watercraft lift.
A need thus exists for a watercraft lift which supports a watercraft without requiring locking of the hydraulic cylinder mechanism.
A need exists for the above type of watercraft lift which supports a watercraft by means of the raising of pivoting booms into a stable and secure orientation in which the pivoting booms can be braced to hold the watercraft lift safely in its raised position.